110 lines
3.3 KiB
Python
110 lines
3.3 KiB
Python
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from collections import defaultdict
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from string import ascii_uppercase
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from grid import Grid
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def main():
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with open("day20.txt") as input_file:
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lines = [l.rstrip() for l in input_file.readlines()]
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maze = Maze(lines, value_factory=str)
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maze.find_portals()
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maze.dumb_print()
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min_steps = maze.count_min_steps(maze.entry, maze.exit)
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print("Min steps:", min_steps)
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class Maze(Grid):
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TILE_PATH = "."
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TILE_WALL = "#"
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ENTRY_DG = "AA"
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EXIT_DG = "ZZ"
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def __init__(self, lines, *args, **kwargs):
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super().__init__(*args, **kwargs)
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self.entry = None
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self.exit = None
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self.portals = {}
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for y, line in enumerate(lines):
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for x, value in enumerate(line):
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self.setv(x, y, value)
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def find_portals(self):
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portals = defaultdict(list)
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for x, y, v in list(self.values_gen()):
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if v in ascii_uppercase:
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rv = self.getv(x + 1, y)
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if rv and rv in ascii_uppercase:
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rrv = self.getv(x + 2, y)
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portal_pos = (x + 2, y) if rrv == Maze.TILE_PATH else (x - 1, y)
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portals[v + rv].append(portal_pos)
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continue
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dv = self.getv(x, y + 1)
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if dv and dv in ascii_uppercase:
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ddv = self.getv(x, y + 2)
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portal_pos = (x, y + 2) if ddv == Maze.TILE_PATH else (x, y - 1)
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portals[v + dv].append(portal_pos)
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for n, p in portals.items():
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if n == "AA":
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self.entry = p[0]
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elif n == "ZZ":
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self.exit = p[0]
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else:
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self.portals[p[0]] = p[1]
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self.portals[p[1]] = p[0]
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def dumb_print(self):
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for y, row in self.g.items():
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for x, v in row.items():
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if (x, y) in self.portals:
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v = "░"
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if (x, y) in (self.entry, self.exit):
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v = "▒"
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print(v, end="")
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print()
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def bfs(self, start, end):
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discovered = Grid(value_factory=bool)
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discovered.setv(start[0], end[1], True)
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parents = {}
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q = [start]
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while q:
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pos = q.pop(0)
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if pos == end:
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return parents
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nears = self.near_objects(pos)
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for near_pos, near_tile in nears.items():
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if near_tile != Maze.TILE_PATH:
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continue
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if discovered.getv(near_pos[0], near_pos[1]):
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continue
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discovered.setv(near_pos[0], near_pos[1], True)
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parents[near_pos] = pos
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q.append(near_pos)
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return None
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def count_min_steps(self, start, end):
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parents = self.bfs(start, end)
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count = 0
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pos = end
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while pos != start:
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pos = parents[pos]
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count += 1
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if pos in self.portals: # One more step to traverse portal.
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count += 1
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return count
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def near_objects(self, p):
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nears = super().near_objects(p)
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for near in list(nears):
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if near in self.portals:
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nears[self.portals[near]] = Maze.TILE_PATH
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return nears
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if __name__ == "__main__":
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main()
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